riscv: Fix "no previous prototype" compile warning in kgdb.c file

Some functions are only used in the kgdb.c file. Add static properities
to these functions to avoid "no previous prototype" compile warnings

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
1 file changed